Complications of Zygomatic Implants: Our Clinical Experience with 4 Cases

Abstract

Zygomatic implants have been used for rehabilitation of the edentulous atrophic maxilla as an alternative to bone grafting for almost two decades resulting in satisfactory clinical outcomes. However, the patients with edentulous atrophic maxilla treated using this technique may present serious complications that could put the prosthetic restoration at risk. Four cases are reported in this paper, one case with a cutaneous fistula in the left zygomatic-orbital area caused by aseptic necrosis at the apical part of the implant, which was treated with the surgical removal of this part, a second case with loss of the right zygomatic implant due to failure of osseointegration and two cases of periimplantitis that resulted in partial and complete removal of the implant, respectively. All patients who had complications were treated without compromising the restoration which remained functional after appropriately modified treatment.

INTRODUCTION

Excessive bone resorption combined with poor bone quality and increased maxillary sinus pneumatization often making it impossible to place conventional dental implants in the posterior maxilla. Various bone augmentation techniques, such as sinus floor elevation and onlay bone grafting, have been described in order to increase the volume of load-bearing bone. Nevertheless, efforts have been made to pursue alternatives to grafting procedures and one of these, especially in the atrophic maxilla, is the use of zygomatic implants. This implant which was initially introduced for the prosthetic rehabilitation of patients with extensive defects of the maxilla caused by tumor resections, trauma or congenital defects was also used in patients with edentulous atrophic maxilla, enabling rehabilitation with sufficient function and improved esthetics (1-5). However, the placement of zygomatic implant is not deprived of risks, since it may involve delicate anatomical structures such as the orbit, and therefore surgical experience is required (6). Additionally, many complications have been reported in the literature, with sinusitis being the most common (7). The aim of this paper is to report and discuss the complications and their treatment after zygomatic implant surgery in 4 cases and to review the contemporary literature on this subject.

Cases report

Case 1

A 37-year-old female patient with generalized periodontitis presented to our clinic. A comprehensive clinical and radiographic evaluation revealed advanced alveolar bone resorption rendering the prognosis of all upper teeth unfavorable. Apart from smoking, the patient was otherwise healthy and very demanding. She strongly preferred an immediate rehabilitation without grafting procedures; therefore zygomatic implants were considered the best treatment for her. Following the extractions of the upper teeth, two zygomatic implants were placed, one on each side, in combination with four conventional implants in the anterior maxilla and an immediate prosthetic restoration was fabricated and adjusted. After one year, the patient presented with a cutaneous fistula in the left zygomatic-orbital area because of aseptic necrosis in the apical part of the left zygomatic implant (Figure 1). In order to deal with this complication without compromising the prosthetic restoration, after the removal of the fistula canal, the apical part of the implant which extruded exteriorly to the zygomatic bone was cut off and removed while the remaining implant and the restoration were retained and were functional with no need for further intervention (Figure 2a, b, c, Figure 3). Ten years after surgery, there were no signs and symptoms of infection in the zygomatic area.

Figure 1.

Cutaneous fistula with suppuration in the left zygomatic-orbital area.

Figure 2.

a) Exposure of the apical part of the implant, b) Surgical site after its
 removal, c) the implant part that was removed.

Figure 3.

The left zygomatic-orbital area, 6 months postoperatively.

Case 2

A 57-year-old female patient with edentulous atrophic maxilla was referred to our clinic for rehabilitation. She had a well-controlled, type-2 diabetes mellitus, treated with metformin, without other health problems or medications. Because of the bilateral advanced bone resorption in the posterior maxilla, the use of two zygomatic implants in combination with conventional implants anteriorly was the treatment of choice followed by fabrication of an immediate restoration supported by the conventional implants only. Four months after surgery, clinical examination of the implants revealed that the right zygomatic one had failed to osseointegrate. A small incision around the implant’s cover screw was performed and the zygomatic implant was removed using dental forceps (Figure 4). The patient did not wish to replace the missing implant with a new one because she considered it a major procedure. However, the remaining implants were successfully osseointegrated and therefore, a permanent restoration extending to the premolar area on the right side, in order to reduce the cantilever effect, was placed (Figure 5a,b). The patient has been followed up for 7 years. So far, no further problem has occurred and the restoration has remained functional.

Figure 4.

Removal of the right zygomatic implant with the dental forceps.

Figure 5.

a,b: Radiographic and clinical image with the final restoration.

Case 3

A 45-year-old male smoker, with no health problems but with generalized advanced periodontitis was treated with two zygomatic implants, one on each side, and six conventional implants anteriorly. Five years after surgery, clinical examination revealed advanced periimplantitis of the left zygomatic implant with severe bone loss that rendered non-surgical treatment unfeasible. Thus, after flap elevation and evaluation of the damage, it was decided to cut off and remove the contaminated part of the implant and leave intact the part which was integrated in the zygomatic bone (Figure 6, 7). Moreover, the fixed prosthetic restoration was modified with the sectioning and removal of the molar area which was supported by the left zygomatic implant in order to remain functional (Figure 8). Five years after surgery, the restoration remained functional and the part of the zygomatic implant which had been left anchored in the zygomatic bone remained asymptomatic.

Figure 6.

Advanced bone resorption around zygomatic implant because of
 periimplantitis.

Figure 7.

Removal of the contaminated implant part without penetrating the sinus
 membrane.

Figure 8.

Panoramic radiograph, showing the rest of the implant remaining integrated
 in zygomatic bone, after making the necessary modifications of the restoration.

Case 4

A 52-year-old healthy male patient was treated in our clinic with a fixed restoration supported by two zygomatic implants and five conventional implants in the anterior maxilla. After almost two years, the patient presented with advanced periimplantitis of the left zygomatic implant, extensive bone resorption and oroantral fistula formation. This complication was treated with the complete removal of the zygomatic implant (Figure 9, 10, 11). There were no signs of sinus pathology in a five year follow- up period.

Figure 9.

Flap elevation revealing the exposed implant threads.

Figure 10.

Removal of the implant using dental forceps.

Figure 11.

Surgical site, with the sinus cavity being exposed, after the removal of the
 implant.

DISCUSSION

In a 15–year period, ten patients (six men and four women, age range: 37-72 years) were treated in our clinic with two zygomatic implants, one on each side, in combination with conventional implants in the anterior maxilla. Complications occurred in four patients, two e zygomatic implants were completely removed, one was sectioned and partially removed and one was treated with removal of its apical part but it remained functional. In conclusion, 3 out of 20 zygomatic implants were lost, resulting in a survival rate of 85%.

The success rate for zygomatic implants obtained by different authors varies between 82% and 100% (1). From the systematic review of 25 studies with a mean follow-up of 42.2 months (range 0–144 months) and a total of 1541 zygomatic implants, Goiato et al. found a survival rate of 97.86% after 36 months (8). This value remained constant up to the last follow-up period. Chrcanovic and Abreu reviewed 42 studies including 1,145 patients and 2402 zygomatic implants. A total of 56 zygomatic implants were reported as failures and the cumulative success rate (CSR) over a 12-year period was 96.7% (6).

The preliminary data show that the zygomatic implant technique is predictable with satisfactory clinical outcomes. Compared with major bone grafting, it is still a less invasive technique and can be used in cases where bone grafts cannot be harvested for some reason (4). Nevertheless, the procedure is associated with serious complications which, although rare, may jeopardize the treatment plan.

The main complication of zygomatic implants is sinusitis which may develop even several years after their placement (7). The reported incidence of sinusitis after zygomatic implant placement ranges from 0% to 26.6% (9, 10). Other complications include oroantral fistula formation, orbital penetration and injury, temporary sensory nerve deficits and vestibular cortical fenestration (5, 6, 10, 11). Post-operatively, periorbital and subconjunctival hematoma or edema, subcutaneous malar emphysema, moderate nasal bleeding for 1–3 days, intraoral soft tissue problems (gingival inflammation, wound dehiscence) and implant failure may occur (5, 6, 10). In patients with pronounced buccal concavities on the lateral aspect of the maxillary sinus, the use of the original technique with an intra-sinus path results in excessive palatal emergence of the implant head leading in a bulky dental bridge at the palatal aspect, which causes discomfort and problems with oral hygiene and speech (4, 5).

Limited intraoperative visibility, complexity of anatomical structures and intricacies of zygomatic curve render this procedure a clinically demanding task, hence, patients have to be informed of possible complications. It seems that during the clinical procedure of implant placement zygomatic-facial nerve is encountered frequently; therefore its injury is possible. The same applies to infraorbital nerve. Due to reflection of the soft tissue over it, sensitivity disorders of the malar skin following implant placement in the zygomatic bone have been reported (6, 11).

In the present paper, four rather minor complications have been reported: a case with a cutaneous fistula in the left zygomatic-orbital area, a case with failure of osseontegration and two cases of periimplantitis, one of these combined with oroantral fistula formation. To the best of our knowledge, there is only one case of bilateral cutaneous fistula after zygomatic implants placement reported by Garcia et al. (12). On the other hand, periimplantitis and oroantral fistula formation are more common complications. From the systematic review of Chrcanovic and Abreu which was mentioned before, 48 cases of soft tissue infection around the implants and 17 cases of formation of oroantral fistulas in a total of 2402 zygomatic implants were found (6).

As far as first case is concerned, it is assumed that bone necrosis caused either by overtorquing or overheating in the apical area of the osteotomy during the drilling procedure due to big depth of the osteotomy for a zygomatic implant, can possibly make irrigation inadequate for cooling at its apical part, thus resulting in aseptic heat necrosis. Based on the time the complication occurred, overtorquing is a more reasonable explanation for this complication. Regarding the second case, many factors can be responsible for failure of osseontegration in dental implants, therefore it can only be speculated that implant-related or local factors were the cause of failure. In the third case, the zygomatic implant was placed at a large inclination angle due to the anatomy of the area. This fact in combination with palatal emergence of the implant head caused problems with oral hygiene resulting in periimplantitis which is the cause of failure. The fourth implant was lost because of an advanced periimplantitis which led to oroantal fistula formation.

The treatment was localized, two of the involved zygomatic implants were completely removed and two were sectioned and partially removed. Moreover, all patients were treated with postoperative antibiotic treatment (Table 1). The management of zygomatic implants complications is a multidisciplinary task. The prosthodontist, who is responsible for the prosthetic restoration, should cooperate with the surgeon in order to find the solution that best meets the patient’s needs: preventing the patient from exhibiting any signs and symptoms and, simultaneously, without compromising the function of the restoration.

Table 1. Complications of zygomatic implants in the 4 cases and their treatment.

	Number of implants placed	Complication	Treatment	Follow up
Case 1	2 zygomatic and 4 conventional implants	Aseptic necrosis after 1 year	Removal of the apical part	10 years
Case 2	2 zygomatic and 4 conventional implants	Failure of osseoinegration / 4 months	Complete removal of the zygomatic implant	7 years
Case 3	2 zygomatic and 6 conventional implants	Periimplantitis after 4 years	Partial removal of the zygomatic implant	5 years
Case 4	2 zygomatic and 5 conventional implants	Periimplantitis after 2 years	Complete removal of the zygomatic implant	5 years

CONCLUSIONS

The use of zygomatic implant in the rehabilitation of the edentulous atrophic maxilla has been considered a viable alternative to bone grafting. However, complications of zygomatic implants, with sinusitis being the most common, can be difficult to treat or can result in loss of the implant; therefore, it should be selectively applied. The four cases reported here, which developed complications, were treated successfully without compromising the prosthetic restoration.